1. Field of the Invention
The present invention is directed generally to a towing hitch, and more particularly to a towing hitch for coupling a farm implement to a truck licensed for public transportation on public roadways.
2. Description of Related Art
Agricultural implements such as plows, hay balers, spreaders, mowers and other such trailers are towed behind an agricultural tractor 8 while in use. The connection between the trailer and the agricultural tractor 8 is facilitated with what is commonly referred to as a three-point hitch 2, which is shown in FIG. 1. As shown, the three-point hitch 2 includes a pair of lift arms 4 that are each independently pivotally coupled to a tail section 6 of the agricultural tractor 8 at a proximate end 7 of the lift arms 4. A connecting arm 11 is used to secure each of the lift arms 4 to an adjustable boom 14x having an elevation that can be adjusted by the agricultural tractor's hydraulic system. A bracket 16a formed at the tail section 6 of the agricultural tractor 8 includes a pin 17 that extends between a pair of braces 18a to receive an upper link arm (FIG. 2b) that is also coupled to the trailer being towed by the agricultural tractor 8.
Agricultural trailers that are to be towed behind agricultural tractors 8 typically include a connector 99 such as that shown in FIG. 2a, for example, comprising at least a pair of laterally extending pins 3. The pins 3 extend outwardly from the connector 99 to cooperate with an aperture 35 formed in each lift arm 4 of the three-point hitch 2 provided to the agricultural tractor 8. Each pin 3 is separated from the other by a fixed distance X, a distance X that can vary from trailer to trailer. To allow agricultural tractor 8 to tow a variety of different trailers having different distances X between the lateral pins 3 of the trailer, and to facilitate coupling of the trailer to the tractor 8, the lift arms 4 of the agricultural tractor 8 are pivotally connected to the agricultural tractor 8 so the lift arms 4 can travel in a plane generally parallel to the ground on which the agricultural tractor 8 rests, as indicated by the arrow 9 in FIG. 1. Thus, to hitch a trailer with the connector 99 in FIG. 2 to the agricultural tractor 8, the lift arms 4 are spread sufficiently apart and the trailer and/or tractor 8 properly positioned relative to the other. The lift arms 4 are then swung back towards each other to engage the pins 3 of the trailer and couple the trailer to the tractor 8. A locking pin serves to prevent the lift arms 4 from sliding off of the trailer pins 3 and causing the trailer to become disconnected from the agricultural tractor 8 when such disconnection is not desired. A chain 11 between the lift arms 4 and the agricultural tractor 8 limits the lateral travel of each lift arm 4 parallel to the ground along arrow 9 to prevent contact between the lift arms 4 and the tires of the agricultural tractor 8, while still allowing the trailer to pivot with respect to the agricultural tractor 8 such as when the agricultural tractor 8 turns.
While FIG. 2a illustrates what is often referred to as a two-point trailer connector, referring to the two pins 3 that establish the connection with a tractor 8, FIG. 2b illustrates a three-point connector 305. As the name implies, the two pins 3 are complemented by an upper link arm 302 that establishes a third connection point with the tractor 8 via communication with the pin 17. A receiver 320 defines an aperture 315 through which the pin 17 shown in FIG. 1 extends while the aperture 315 of the receiver 320 is coaxially aligned with similar apertures formed in the pair of braces 18a. 
Farmers are often required to transport an agricultural trailer such as those mentioned above to a remote field located far away from the location where said trailer is stored. Further, agricultural trailers are subjected to harsh environments, and require regular maintenance to function properly, particularly at the beginning and end of each crop cycle when the trailer is removed from and returned to storage. Towing the agricultural trailer behind an agricultural tractor 8 to a remote field or a distant maintenance facility can be very time consuming due to the slow top speed of agricultural tractors 8, which are not designed or licensed for passenger transportation. While some maintenance facilities offer to transport the agricultural trailer and take it to the remote field or into the distant maintenance facility, such a service is expensive due again to the time required for such transportation with an agricultural tractor 8.
Accordingly, there is a need in the art for a trailer hitch to couple an agricultural trailer to a vehicle other than an agricultural tractor for transporting the agricultural trailer over public roadways. The vehicle can be licensed for public transportation on public roadways. Further, the trailer hitch can optionally accommodate trailers having a pair of laterally extending pins separated by a range of distances, optionally allow for vertical relative positioning of a portion of the trailer hitch and the trailer, and optionally be interchangeable with conventional hitches for towing traditional trailers over public roadways.